The present invention relates to a braking device for a window screening arrangement, the screening arrangement being intended for mounting in a window aperture defined between a top member, a bottom member and two side members, and including a body of screening material which in an unscreening position is rolled up, collapsed or pleated at the top member and which in a free end is connected with at least one hollow bar extending substantially in parallel with the top and bottom members between the side members substantially throughout the width of the window aperture. A parallel guidance system includes two cords in reverse mounting, each cord being passed from a first fixture at the top member along one side member, through the hollow bar and along the other side member to a second fixture at the bottom member, and a cord tightening device being provided in connection with at least one fixture, in which the braking device includes at least one braking member for retaining the hollow bar in at least one screening position.
In its simplest form, an arresting device may consist of side rails positioned at the window aperture side members and include a number of downwards facing recesses for engagement with the bar or pins connected therewith.
In order to retain the bar at the free end of a screening arrangement in a position in which the window arresting or braking devices have been contemplated.
However, such a design is not suitable for all fields of usage.
FR patent application No. 2 615 240 and U.S. Pat. No 785,806 represent one category of braking devices, in which the braking force of the braking device is adjusted by tightening the cords of the parallel guidance system. As a consequence of the design, operation of the screening arrangement may be difficult, as the braking force has to be surmounted in order to move the screening arrangement between the top and bottom members of the window aperture. This is particularly the case in roller blinds including a roller bar, the spring-bias of which the braking force has to counteract.
U.S. Pat. No 612,606 represents another category of braking devices in which friction shoes at each end of the bottom bar cooperate with the side members of the aperture in order to retain the bar in the desired position. As the friction shoes are biased by springs placed in the bar, the latter have to be deactivated in order to move the screening arrangement. Although operational comfort is provided once the friction shoes have been retracted from their frictional engagement with the side members, this arrangement is complicated and thus costly and cumbersome to produce and mount.
EP patent No. 0 725 885 discloses a roller blind including a braking device of the above stated kind which alleviates many of the disadvantages of the prior art arrangements. The braking device of this reference includes a friction member mounted in the bottom bar, in which at least one reversing member provides for at total change of the direction of the corresponding cord. Although this arrangement has turned out to work efficiently, it is only comparatively simple, as the threading of the cords has to be carried out properly in order to provide the desired frictional braking force. Furthermore, due to the position of the braking device inside the bottom bar, it is virtually impossible to substitute for a defective braking device or provide new cords in the parallel guidance system without discarding the entire window screening arrangement, or at least the bottom bar.
On this background, it is the object of the present invention to improve a braking device of the above stated kind, in which the manufacture and mounting of the braking device is less complicated and in which the parts of the window arrangement may easily be exchanged.
For this purpose, a braking device according to the invention is characterized in that the at least one braking member of the braking device is mounted substantially stationarily on at least one of said cords and is intended, in a screening position, to engage with said hollow bar.
By this simple design, the braking device and consequently the entire window screening arrangement is simpler and cheaper to manufacture and mount. Furthermore, the braking device may be provided separately, possibly together with the parallel guidance system. It is thus easy to substitute parts of the screening arrangement and it is possible to mount the braking device subsequently on existing screening arrangements not being provided with such a device. Eventually, an indication of the desired screening position is obtained at the moment of engagement between the braking member or members and the bar, which may be advantageous in order to attract the user""s attention when the screening arrangement has reached its bottom position to prevent further downwards movement of the screening arrangement.
In a preferred embodiment, each braking member is designed as a symmetrical body, the axis of symmetry of which is substantially parallel with the corresponding cord. By this embodiment, a safe engagement between the braking device and the bar is secured at all times, independently of the rotation or twisting of the cords.
In a constructionally simple embodiment the braking member or members may be designed as hollow body for accommodation of the cord.
Preferably, the braking device comprises at least one pair of braking members placed opposite each other at substantially the same distance from the top member of the window aperture. By this design, the load on the cord system and the tightening means is symmetrical and an aesthetically attractive arrangement is obtained.
Further features and advantage will appear from the present specification.
In another aspect, the braking device is part of a window screening arrangement.
The invention will now be explained in detail with reference to the schematic drawings, in which